Convergence of networks, services and devices has facilitated increase in access to online digital media content by users which in turn has facilitated illegal copying and distribution of digital media. Illegal copying and distribution of original digital media content with or without modifications can take place in numerous ways including, but not limited to, peer-to-peer (P2P) file sharing systems, websites that accept user generated content (UGC) or copies in compact disks (CDs) and digital video disks (DVDs). For example, video signals are highly susceptible to attacks such as frame averaging, frame swapping, frame dropping, statistical analysis and interpolation which results in tampering the original video content and making it available as some other video content. Further, frames in the video signal, like images, are susceptible to various image processing attacks such as joint photographic experts group (JPEG) compression, sharpening, lightening, darkening, noising, blurring, distortion, rescaling, rotation, cropping, jittering and mosaic attacks. In addition, high volume of uploaded media content in social networking and media sharing websites makes it difficult to monitor all the uploaded content for copyright infringement, piracy and illegal distribution.
Digital watermarking is currently adopted for copyright protection of digital media content. Digital watermark is a visible or an invisible watermark pattern inserted into digital media which facilitates identifying copyright owner of the digital media. Conventionally, watermark pattern is embedded into original video content in spatial domain which includes embedding identical or non-identical watermarks in frames of the video content. Watermark pattern may also be embedded into original video content in frequency domain i.e. in discrete wavelet transform (DWT) bands, using techniques of multi-resolution signal decomposing, using discrete fourier transform (DFT), using discrete cosine transform (DCT), and using DCT based perceptual watermarking methods.
However, the above-mentioned watermarking techniques are prone to watermark attacks that are aimed at detecting, distorting and destroying the embedded watermark pattern. Further, the above-mentioned techniques result in drawbacks because of large volume of video data and inherent redundancy between the frames which poses difficulty in identifying transition between the frames. For example, if identical watermark pattern is embedded in the frames, an attacker can get information regarding the video content by colluding with frames from different scenes of the video. Further, if non-identical watermark pattern is used for each frame, then attacker may remove watermark pattern by identifying motionless regions in successive video frames and comparing and averaging the frames statistically.
Embedding watermark in original video content, therefore, makes watermark pattern susceptible to various image and video watermarking attacks and attackers can use embedded information for detecting and destroying or degrading watermark content embedded into videos. Moreover, the video signals are highly susceptible to piracy attacks including frame averaging, frame dropping, frame swapping, statistical analysis, interpolation, time editing, inter video correlation, intra video correlation etc. which degrades or removes the embedded watermark from the video content. In addition, perceptual fidelity is an important aspect of watermarking process. Due to three-dimensional characteristic of video data, maintaining imperceptibility of the watermark content is a considerably difficult task. Further, conventional techniques offer difficulty in detecting watermark pattern accurately or efficiently if there is scene dropping in the original watermark content.
In light of the above, there is a need for a system and method for optimized watermarking of each scene of video content using visual cryptography. There is a need for a system and method for watermarking averaged scene images of video content employing visual secret sharing in an imperceptible way. There is a need for a robust, secure and efficient watermarking technique which is useful for detecting copyright infringement of each scene of a video content.